Johnny Ball, 74, presented children’s TV shows such as Think Of A Number. Here he talks to Metro about donning sequins and a bow tie for the new series of Strictly Come Dancing and what he thinks of children’s TV today.

Johnny Ball is one of this year’s Strictly Come Dancing hopefuls (Picture: Getty)

Why did you decide to do Strictly Come Dancing?

They asked me and I thought I couldn’t turn it down and neither could I wait another 15 years for them to ask me again.

Was it a difficult decision?

Not at all. I wanted to do it because it’s a great show and a great leveller – it’s all about effort and work and setting your heart on doing well. It’s been tremendous so far.

Are you doing this for the older viewer?

I want to do well irrespective of my age – I want to show if you keep fit and make an effort you can do amazing things regardless of what the numbers tell you. I read an article about how dancing can keep Alzheimer’s at bay so maybe that’s what I’m doing.

Yes and no. If I win, it means they’ve put 13 stumblebums up against me. At this stage I don’t know if anyone expects to win it, we’re all just settling in. I don’t see myself as the novelty older person or clown figure: I really think I can compete in terms of dancing. I’m the oldest contestant ever but I want to convince people I’m not the age I am.

Has your daughter, Zoe, given you any tips?

Not with the dancing. She’s just told me to enjoy it and go with the flow. Everyone who’s gone on before comes out the other end saying it’s a fantastic experience.

What was it like watching her do the show?

Fantastic – she did so well the first week and was one of the best dancers so we were all very proud of her.

She presents the spin-off show – does that mean you’ll be getting preferential treatment?

Absolutely not. She didn’t know I was doing it until two days before the line-up was announced. They wanted to have a camera there when they told her I was doing it but it never happened. I don’t want anyone to have the idea Zoe said: ‘Please have my dad,’ because that didn’t happen.

What do you think of the state of children’s TV today?

I don’t watch it any more. I’ve moved on. No one does the programmes I did. I started as a stand-up comic and then wrote jokes for programmes such as Play Away and found I could present information to people in an accessible way – I did the theory of relativity three different ways in my shows.

What was your first stand-up gig like?

I ran out of material on my first gig and ended up calling the bingo as well. I put in every gag I could think of but it all seemed to go well. The next gig was also a success, then I died for the next ten. Without those first successes I’d have given it up. I did it for 12 years – all the cabaret clubs in the north. I loved doing it but it didn’t transfer to TV. Some acts translated better to TV than others. Les Dawson was funnier on TV than he was in the clubs. Then I changed tack and got into factual TV. Maths was my hobby and it became a joy to do programmes about it.

What’s the worst stand-up gig you did?

I don’t specifically remember any bad audiences. I always said: ‘If an audience gives me five minutes of their attention and I have a problem, it’s my fault.’ Comedians who have bad nights in good conditions don’t remain comics for very long.

Have you been recognised anywhere unusual?

I guy came up to me in Oxford Street and said: ‘You were my education, you were,’ then as I said thank you and turned away he shouted: ‘Big Issue!’

Have you got any favourite maths-related trivia?

Humans are around 50 per cent DNA-identical to a banana. And humans eat more tuna each year than the total weight of the population of Great Britain but British spiders alone also eat more than the total weight of the population of Great Britain.

Have you got any ambitions left to fulfil?

I have always said the way I made programmes for kids in the 1980s would have worked for any audience. In fact towards the end, our massive figures included more than 60 per cent adults. I still believe the method I used could work today and that I could do it. My ambition is to never really retire, as life is too short.

What are people’s misconceptions of you?

I’m just thrilled that after being off TV for 20 years people are still so nice to me. They remember the shows I did and a lot of people grew up watching them. Every day someone says I was part of their childhood, which is lovely. I am very lucky.